export function sayHi(greeting, name) {
  console.log(`${greeting}, ${name}`)
}

export let PI = 3.14
export var a = 123
export const b = 234

export let x=1, y=2, z=3

export class MyClass {}

let x2 = 10
// export x2 // 错
export {x2} // 聚合导出
export {x2 as X2} // as 把什么当成什么，X2是外部的名字


// if (true) {
//   export ... // 错
// }